The present disclosure herein relates to a material for an organic electroluminescent device and an organic electroluminescent device including the same, and more particularly, to a material for an organic electroluminescent device having high emission efficiency and long life (e.g., long lifespan) and an organic electroluminescent device including the same.
In recent years, organic electroluminescent (EL) displays as one kind of image displays have been actively developed. Unlike liquid crystal displays and the like, organic EL displays are so-called self-luminescent displays which display images by emitting light from a luminescent material including an organic compound in the emission layer through recombination of holes and electrons injected from an anode and a cathode in the emission layer.
An example of an organic EL device existing in the art is an organic EL device which includes an anode, a hole transport layer disposed on the anode, an emission layer disposed on the hole transport layer, an electron transport layer disposed on the emission layer, and a cathode disposed on the electron transport layer. Holes injected from the anode are injected via the hole transport layer into the emission layer. Meanwhile, electrons are injected from the cathode, and then injected via the electron transport layer into the emission layer. The holes and the electrons injected into the emission layer recombine to generate excitons within the emission layer. The organic EL device emits light generated by deactivation radiation of the excitons. Organic EL devices are not limited to the above-described configuration but may be changed to various suitable forms.
When organic EL devices are applied in display apparatuses, the high efficiency and long life (e.g., long lifespan) of the organic EL device are required. The driving voltage is high and the emission efficiency is insufficient in an organic EL device—particularly in a blue emission region when compared to a green emission region and a red emission region. To realize the high efficiency and long life of an organic EL device, ways of increasing the normalization, stabilization and durability of the hole transport layer have been examined.
As a hole transport material utilized in a hole transport layer, various compounds such as an aromatic amine compound have been utilized. However, issues related to resolving the short life (e.g., short lifespan) of the device remain. As a useful material for increasing the life (e.g., the lifespan) of the organic EL device, for example, an amine derivative substituted with an aryl group or a heteroaryl group has been suggested. However, an organic EL device utilizing the above-mentioned material has insufficient emission life. An aromatic amine compound having 4-dibenzofuran has been suggested as a charge transport material. However, the aromatic amine compound suggested has a high molecular weight, and defects concerning thermal stability may arise during the manufacture of an organic EL device. Thus, an organic EL device having higher efficiency, thermal stability and long emission life is required (or desired) at present. Particularly, since the emission efficiency of an organic EL device in a blue emission region is lower than in a red emission region and a green emission region, an increase in the emission efficiency in the blue emission region is required (or desired).